1. Field of the Invention
The present invention relates to a testing method for testing a semiconductor device and, particularly, to a testing method for confirming a connecting state of signal terminals provided in a semiconductor device.
2. Description of Related Art
As a method for confirming a connecting state of signal terminals provided in a semiconductor, it has been usual to supply a current to each signal terminal and measure voltage values at the respective signal terminals. Such conventional testing method will be described with reference to FIG. 1. In FIG. 1, an LSI 101 is used as a semiconductor device which has a plurality of signal terminals 103-1 to 103-n and a plurality of V.sub.DD terminals 105-l to 105-n to which a power source voltage is applied. The signal terminal 103 -i (i=1.about.n) is connected to the V.sub.DD terminal 105-i through a protective diode 104a-i and to a GND terminal 106-i through a protective diode 104b-i. A case where the signal terminal 103-1 is a terminal to be measured will be described.
First, the voltage values of the V.sub.DD terminals 105-1 to 105-n are made 0V. Then, a constant voltage is applied from a tester 102 to the signal terminals other than the signal terminal 103-1 which is the terminal to be tested. Thereafter, a current is supplied from the tester 102 to the signal terminal 103-1 and a voltage value at the signal terminal 103-1 is measured.
When the measured voltage value at the signal terminal 103-1 is 0V, it is judged that the signal terminal 103-1 is short-circuited to the V.sub.DD terminal 105-1 or the GND terminal 106-1. When the measured voltage value at the signal terminal 103-1 is a clamp voltage (usually, equal to or higher than 1V), it is judged that the signal terminal 103-1 is opened. When the measured voltage at the signal terminal 103-1 is equal to the voltage value applied to the signal terminals 103-2 to 103-n other than the signal terminal 103-1, it is judged that the signal terminal 103-1 is short-circuited to at least one of the signal terminals 103-2 to 103-n. When the measured voltage of the signal terminal 103-1 is 0.3.about.0.6V which is a voltage drop due to the forward characteristics of the protective diodes 104a-1 and 104b-1, it is judged that the signal terminal 103-1 is connected normally.
FIG. 2 shows an example of the testing time in the prior art testing method mentioned above. The mass-productivity of semiconductor device is becoming more and more important with the recent expansion of semiconductor market. Therefore, in order to realize the required mass-productivity of semiconductor device, a speedup of not only the manufacture of semiconductor device but also the test thereof is indispensable. In the prior art testing method, however, it takes about several milliseconds to test the connecting state of each signal terminal of the semiconductor device. Therefore, in order to test a semiconductor device which has a more complicated structure and an increased number of pins, a considerable time is necessary and the speedup of testing becomes difficult.